Petroleum refining process



Jan. 3, 1961 R. E. MANLEY 2,967,146

PETROLEUM REFINING PROCESS Filed Dec. so, 1957 s sheets-sheet 1 -T1c'l.

Jani 3, 1961 R. E. MANLEY 2,967,146

PETROLEUM REFINING PROCESS Filed Dec. 30, 1957 3 Sheets-snee?l 2 MMS l I I I l O l0 2o 3o 40 5o eo A Vl (Increase in Vl on Hljglggenh'on) Jan. 3, 1961 Fil'ed Dec 30, 1957 Decrease In Molecular Weg h l' R. E. MANLEY 2,967,146

- PETROLEUM REFINING PROCESS A Turi' Increase .in VI onHqdroqenah'on 3 Sheets-Sheet 3 Robert E. Manley, Yonkers, N.Y., assigner to Texaco Inc., a corporation of Delaware Filed Dec. 30, 1957, Ser. No. 706,215

8 Claims. (Cl. 208-444) This invention relates to a petroleum refining process. More particularly, this invention relates to the treatment of petroleum residua and petroleum fractions in the lubricating oil range. Still more particularly, this invention relates to aprocess for the upgrading of petroleum fractions into more valuable materials.

In the refining of petroleum fractions, such as petroleum distillates and residua, for the production of lubricating oils one operation conventionally employed is a solvent refining operation. In a solvent refining operation the petroleum fraction undergoing treatment is contacted with a liquid selective solvent for the more aromatic constituents which is at least partially immiscible with the petroleum fraction undergoing treatment under 'the conditions of contacting. From the solvent refining operation there is recovered a rafiinate phase or refined lubricating oil fraction, comprising the more parafiinic constituents of the petroleum fraction undergoing treatment, and an extract phase or extract fraction (after the removal of the selective solvent therefrom) comprising the more aromatic constituents of the petroleum fraction undergoing treatment. This extract fraction possesses properties and characteristics, eg., low viscosity index, which renders it less desirable and useful as a lubricating oil. Accordingly, it has been a practice heretofore to dispose of the resulting solvent refined extract fraction by burning as fuel, or by catalytic conversion into lower molecular weight material, e.g., gasoline constituents or as cutter stock by addition to asphalt and asphalt-like materials.

Accordingly, in view of the foregoing it is an' object of this invention to provide an improved process for. the refining and treatment of petroleum fractions, residua and/or petroleum distillate fractions.

Still another object of this invention is to provide a process for the upgrading of petroleum extract fractions such as are produced in the solvent refining of petroleum into more valuable products.

Still another object of this invention is to provide a method of increasing the availability of lubricating oils.

Yet another object of this invention is to provide a process for the production of naphthene base lubricating oils and the like.

How these and other objects of this invention are accomplished will become apparent in the light of this disclosure made with reference to the accompanying drawings wherein Fig. l is a block fiow diagram which sets forth operational steps in the practice of this invention; and wherein Figs. 2 and 3 graphically illustrate the advantages obtainable in the practice of this invention.

In accordance with this invention extracts derived from the solvent refining of petroleum fractions, particularly al deasphalted or relatively asphalt-free petroleum residuum or petroleum distillate fraction which has also 4been dewaxed, as by solvent dewaxing, are c'ontatcs Patent O i 2,967,146 Patented Jan. 3, 1961 vetted into more valuable products, such as lubricating oils, by hydrogenation.

More particularly, it has been discovered that a petroleum fraction, such as a petroleum residuum or petroleum distillate fraction, after deasphalting or decarbonation, if required, followed by solvent dewaxing' of the asphalt-free or the resulting deasphalted or decarbonized oil, and after separation by solvent refining into a relatively more parafiinic, less aromatic raffinate fraction particularly useful as lubricating oil and a relatively less parafiinic, more aromatic extract fraction, is converted after hydrogenation into a useful and a valuable naphthene base lubricating oil.

Referring now to the drawing, particularly Fig. l thereof, as indicated therein a raw waxy petroleum distillate or a petroleum residuum such as may be derived by distillation from a crude oil, after deasphalting or decarbonation, if necessary for the removal of carbonaceous material, such as asphalt, therefrom is subjected to a dewaxing operation, such as a solvent dewaxing operation, with the resulting production of a slack Wax which is separately removed as product, as indicated, and a relatively asphalt-free dewaxed oil. As indicated in Fig. 1 the asphalt-free, dewaxed oil is then subjected to solvent refining by contact with a liquid selective solvent which selectively dissolves the more aromatic hydrocarbons therefrom.

As a result of the above-indicated solvent refining operation there is recovered as the raffinate phase a refined oil having properties, e.g., relatively high viscosity index which renders it suitable, as is, or after conventional finishing operations, such as clay contacting and filtering or hydrofinishing, as a lubricating oil. There is also recovered from the solvent'refining operation an extract phase comprising liquid selective solvent containing the more aromatic constituents of the oil undergoing treatment dissolved therein. This extract phase, after the removal of the selective solvent therefrom, yields an extract oil which is characterized by a relatively increased proportion of more aromatic hydrocarbons as compared with the substantially asphalt-free dewaxed oil charged to the solvent refining operation and possesses a relatively vlow viscosity index, as compared with the raffinate, and

therefore is less valuable as a lubricating oil. This ex tract oil, in accordance with this invention, is then subjected to hydrogenation in the presence of a suitable hydrogenation catalyst whereby the more aromatic constituents thereof are converted to more saturated, 'naphthenic type hydrocarbons. Also, during the hydrogenation operation the more unsaturated constituents of the vnaphtha, etc., which might have been formed due to hydrocracking during the hydrogenation operation is subjected to fractionation, as by atmospheric or vacuum distillation, into various lboiling point fractions as required and/or if desired. The resulting fractionated hydrogenated oil is useful, as is, as a lubricating oil because of its improved viscosity index, or might then be acid treated and neutralized and recovered as finished product or, prior to these finishing operations, might be recycled or returned to the hydrogenation zone or operationV for a more complete hydrogenation of the more unsaturated and aromatic constituents thereof for the preparation of specialty lubricating oils.

Accordingly, as disclosed herein, a feed suitable for use in the practice of this invention must be a substantially asphalt-free, dewaxed and solvent refined extract fraction. When required, as would be in the case where an asphaltic petroleum residuum or heavy carbonaceous distillate fraction is being processed in accordance with the practice of this invention, a suitable decarbonation or deasphalting operation is employed for the preparation of the initial asphalt-free charge oil.

The so-called propane deasphalting process is particularly suitable for the preparation of a substantially asphalt-free charge oil. ln the propane deasphaltmg process a liquefied normally gaseous hydrocarbon, such as ethane, propane, n-butane, isobutane, pentane and/or isopentane, or suitable mixtures thereof, Vis employed to contact the asphaltic or carbonaceous petroleum fraction undergoing treatment at or below the critical temperature of the liquefied normally gaseous hydrocarbon employed as the deasphalting solvent. The contacting operation may be batch (combination of mixer-settler) or continuous (tower or the like), either concurrent or countercurrent liquid-liquid contact. In the deasphalting operation the liquefied normally gaseous hydrocarbon solvent employed preferentially dissolves the less asphaltic, less solid, less carbonaceous constituents of the petroleum -residuum leaving behind these asphaltic materials substantially undissolved. These asphaltic materials are then separately recovered as product. The deasphalting operation yields a substantially asphalt-free oil which is particularly suitable for upgrading in accordance with the practice of this invention.

A deasphalted oil, such as may be produced by the propane deasphalting of an asphaltic petroleum residuum described hereinabove, is then subjected to a suitable dewaxing operation, such as solvent dewaxing. In a solvent dewaxing operation a liquid solvent which is a preferential solvent for the liquid oil constituents of the oil and which exhibits substantially no solvent power for the waxy constituents thereof under the conditions of contacting is employed to separate the waxy constituents lfrom'the non-waxy constituents of the deasphalted oil.

A particularly suitable dewaxing solvent is a mixture of -an aromatic hydrocarbon containing from C6 through C8, inclusive, carbon atoms per molecule, e.g., benzene, toluene, or mixtures thereof, and an aliphatic ketone having from 2 to 8, inclusive, carbon atoms per molecule, such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone or mixtures thereof. For example, a suitable dewaxing solvent comprises an aromatic hydrocarbon such as toluene and an aliphatic ketone such as methyl ethyl ketone in the amounts 40-60% vol. and 60-40% vol., respectively. The solvent dewaxing operation is carried out at a suitable low temperature, usually a temperature in the range |30 F. through 50 F., at least sufficient to obtain the removal of wax to the desired extent from the oil undergoing dewaxing. Solvent dewaxing at a temperature low enough to yield a dewaxed oil having a pour point of at least about F., preferably at least about 0 F., is usually satisfactory. ,There results from the solvent dewaxing operation a substantially asphalt-free dewaxed oil.

Following the dewaxing operation the resulting substantially asphalt-free, dewaxed oil is subjected to solvent refining. In the solvent refining operation the oil undergoing treatment is subjected to liquid-liquid contact with a selective solvent which preferentially dissolves the more aromatic constituents from the oil undergoing treatment. It is a characteristic of the selective solvent employed that it is partially miscible with the oil undergoing treatment so that during the solvent refining operation there are formed two phases, a raffinate phase containing substantially only a solvent refined oil having a reduced amount or proportion of aromatic hydrocarbons as compared to the oil charged to the solvent refining operation, and an extract phase or mix comprising selective solvent and dissolved therein extract or extracted oil having a relatively increased proportion or amount of more aromatic hydrocarbons as compared with the charge oil.

Theaforesaid solvent refining operation may be carried out stagewise (combinations of mixer-settler) or continuously in a suitable contacting apparatus, e.g., packed or plate tower, rotating disc contactor, either concurrently or countercurrently. Selective solvents which are suitably employed include furfural, phenols (Selecto) liquid sulfur dioxide, nitrobenzene,/3,dichloroethylether (Chlorex), dimethylformamide and the like.

The resulting solvent refined oil or raffinate, having an increased viscosity index and other improved characteristics relative to the charge oil, is separately recovered as product. The extract phase or mix, after the removal of the selective solvent therefrom, has characteristics which render it less desirable than the rafiinate, e.g., lower viscosity index, as a lubricating oil. The extract oil is then further treated in accordance with this invention.

Following the solvent refining operation, after the removal of the selective solvent from the extract phase, the resulting substantially asphalt-free, dewaxed extract is subjected to hydrogenation or hydrorefining. The hydrogenation operation is carried out under relatively mild conditions such as at a temperature in the `range 600-850 F., a pressure in the range 50G-3,000 p.s.i.g., more or less, and a space velocity in the range 0.1-5.0. Preferably, a solid type hydrogenation catalyst is employed in the hydrogenation operation. Suitable solid type hydrogenation catalysts include metals of groups VI and VIII of the periodic table, their oxides, sulfides or mixtures thereof. A nickel sulfide-tungsten sulfide hydrogenation catalyst has been found to be satisfactory, such as a nickel sulfide-tungsten sulfide catalayst having the composition represented by the empirical formula lNiS-0.75WS2. A molybdenum sulfide-containing hydrogenation catalyst is also satisfactory. Cobalt molybdate is also a suitable solid type hydrogenation catalyst.

Following the hydrogenation operation there is recovered a hydrogenated extract which is particularly useful as an industrial oil. During the hydrogenation operation the viscosity index is increased significantly and both vlscosity and molecular weight are reduced to a level comparable with that normally found in the typical naphthene base Gulf Coast type distillate lubricating oil fraction, thereby rendering the resulting hydrogenated extract suitable as a lubricating oil.

Following the hydrogenation operation the resulting hydrogenated extract is then fractionated to remove any small amount of relatively low boiling hydrocarbons which might have been formed during the hydrogenation operation due to hydrocracking. Following the removal of these low boiling materials the hydrogenated extract 1s then, if necessary or desirable, fractionated into desired fractions according to boiling point range and/or viscosity. This fractionation operation may be desirable if a relatively wide boiling charge stock had been initially employed in the process. If a relatively narrow boiling charge stock had been employed mere stripping to remove any low boiling lower molecular weight hydrocarbons which might have been formed during the hydrogenation operation is suflicient.

Following fractionation the hydrogenated extract is then subject to suitable finishing operations, such as acid treatment and neutralization and/or clay contacting or hydrofinishng. In the hydrofinishing operation the extract, such as after acid treatment and neutralization is contacted with gaseous hydrogen under relatively very mild conditions, e.g., temperature in the range 40G-650 F. at a pressure in the range 30C-3,000 p.s.i.g., more or less. Hydrogenation catalysts suitable for use in the hydrofinishing step include those mentioned hereinabove in connection with the hydrogenation operation. However, in the hydrofnishing step it is preferred to employ a metallic catalyst such as Raney nickel, platinized charcoal, or any of the various noble-metal-containing (e.g. Pt-containing) composite catalysts such as a composite catalyst comprising alumina, platinum and 'Combined halogen, e.g., Platformer catalyst.

The advantages of carrying out the practice of this invention as indicated in Fig. 1 of the drawing, that is, hydrogenating a substantially asphalt-free dewaxed extract from a solvent refining operation with the resulting production of a naphthenc base oil, are graphically illustrated in Figs. 2 and 3 of the drawing. As indicated in Fig. 2, hydrogenation of a raw waxy distillate (i.e., a waxy petroleum fraction which has not been dewaxed and solvent refined) or a deasphalted residuum results in a drastic reduction in viscosity for a given or required viscosity index (V.I.) improvement. Fig. 2 indicates, however, that a hydrogenated extract from a solvent refining operation, such as would be equivalent to the naphthene base oil indicated therein, exhibits a viscosity reduction which is relatively less severe, particularly as compared with the viscosity reduction experienced by the other illustrated petroleum fractions which were not treated in accordance with the practice of this invention.

Fig. 3 of the drawing likewise illustrates that untreated petroleum fractions, such as waxy distillate fractions which have not been solvent refined, or a merely deasphalted residuum undergo a marked decrease in molecular weight, thereby indicating a substantial amount of hydrocrackng, during a hydrogenation operation, to ncrease the viscosity index of the petroleum fraction undergoing treatment and otherwise improve its properties as a lubricating oil. However, a petroleum extract which has been deasphalted, dewaxed and recovered from a solvent rening operation kdoes not exhibit as severe a reduction in molecular weight (that is, does not experience excessive hydrocracking) during a hydrogenation operation to improve its viscosity index and its properties as a lubricating oil.

Accordingly, as indicated in Figs. 2 and 3 of the drawing a petroleum fraction having a particular boiling point range and viscosity is relatively unchanged with respect to these properties provided this petroleum fraction, after deasphalting if necessary, is dewaxed and solvent refined, followed by hydrogenation of the resulting dewaxed extract. Accordingly, when a particular waxy distillate fraction is treated in accordance with the practice of this invention substantially 100% of this fraction is recoverable as a lubricating oil having a viscosity and boiling point range (molecular weight) substantially unchanged with respect to the initially charged waxy distillate, For example, in accordance with the practice of this invention a viscosus waxy distillate, eg., equivalent to SAE 60, after solvent dewaxing and solvent refining, there is produced a dewaxed solvent refined oil (raffinate) having a molecular weight substantially unchanged and a viscosity in the same SAE range and the resulting dewaxed extract, after hydrogenation, has been reduced to a level of viscosity and molecular weight comparable to the normal ranges found in naphthene base lubricating fractions. As a result of the practice of this invention the amount of a satisfactory, relatively high V.I. lubricating oil recoverable from a dewaxed lubricating oil fraction is substantially increased, e.g., 100%, whereas the originally less desirable, low V.I. aromatic hydrocarbons make up about 30-50% of the lubricating oil undergoing treatment.

In the practice of this invention the hydrogenation of the low V.I. relatively asphalt-free, dewaxed extract oil is carried out until the viscosity index of` the oil is substantially increased and improved, at least by about 20 V.I. numbers, such that the viscosity index of the resulting hydrogenated extract oil is at least 20 points, preferably in the range 50-80 points, more or less, above that of the dewaxed extract fraction.

As will be apparent to those skilled in the art many changes, substitutions and alterations are possible without departing from the spirit or scope of this invention. Further, the above-described hydrogenation operations,

-i'.e. hydrorening or hydrogenation of the substantially asphalt-free, dewaxed extract and the hydrofinishing of the resulting hydrogenated extract, as indicated, are carried out under suitable conditions of temperature and pressure, hydrogen recycle rate, space velocity and the like necessary to effect the desired changes in the extract oil and hydrogenated extract oil undergoing treatmen-t. Suitable conditions for effecting hydrogenation or hydrorefining of the extract oil and hydrofinishing of the resulting hydrogenated extract oil are set forth by Cole et al., U.S. Patent 2,779,713 issuedv January 29, 1957, the disclosures of which are herein incorporated and made part of this disclosure.

I claim:

1. A method of treating an asphalt-free waxy hydrocarbon fraction which comprises solvent dewaxing said fraction to yield a dewaxed oil, solvent refining said dewaxed oil by contact with a liquid selective solvent for aromatic hydrocarbons which is at least partially immiscible with said oil to produce a raffinate fraction having a relatively high viscosity index and a reduced aromatic content and an extract fraction having a relatively low viscosity index and an increased aromatic content, recovering said raflinate fraction, hydrogenating said extract fraction to improve substantially its viscosity index by at least about 20 V.I. numbers, fractionating the resulting hydrogenated extract fraction to remove therefrom relatively low boiling hydrocarbons and recovering the resulting fractionated hydrogenated extract fraction as a lubricating oil product.

2. A petroleum refining process which comprises contacting a petroleum residuum with a deasphalting solvent to deasphalt said residuum with the resulting production of a deasphalted oil, solvent dewaxing said deasphalted oil, solvent refining the resulting deasphalted dewaxed oil to yield an extract having a relatively low viscosity index and a relatively high aromatic content as compared with said deasphalted dewaxed oil, hydrogenating said extract to increase substantially its viscosity index by at least about 20 V.I. numbers and recovering at least a portion of the resulting hydrogenated extract as a lubricating oil product.

3. A process in accordance with claim 2 wherein said hydrogenation is carried out at a temperature in the range 60G-850 F. and a pressure in the range 750-3,000 p.s.i.g. in the presence of a solid hydrogenation catalyst.

4. A petroleum refining process which comprises de- .waxing an asphalt-free waxy petroleum distillate fraction to produce a dewaxed oil, solvent refining said dewaxed oil to yield an extract having a relatively low viscosity Iindex and a relatively high aromatic content as compared with said dewaxed oil, hydrogenating said extract to increase the viscosity index of the resulting hydrogenated extract at least twenty viscosity index numbers over the viscosity index of said extract before hydrogenation and recovering at least a portion of the resulting hydrogenated extract as product.

5. A petroleum refining process which comprises solvent dewaxing an asphalt-free waxy petroleum fraction to yield a dewaxed oil, contacting said dewaxed oil with liquid furfural to recover therefrom as extract an extract fraction having a relatively low viscosity index and a relatively high aromatic content as compared with said dewaxed oil, hydrogenating said extract fraction to increase its viscosity index by at least 20 numbers V.I. and recovering at least a portion of the resulting hydrogenated extract fraction as product.

6. A process in accordance with claim 5 wherein the resulting hydrogenated extract fraction is subjected to hydrofinishing at a temperature in the range 40G-650 F. and a pressure in the range 750-3,000 p.s.i.g. to improve the oxidation stability of the aforesaid hydrogenated extract fraction.

7. A petroleum refining process which comprises deasphalting a petroleum fraction in the lubricating oil boiling range to yield a deasphalted oil, dewaxing said deasphalted oil to produce a dewaxed oil, solvent refining said dewaxed oil to yield an extract having a relatively high aromatic content as compared with said dewaxed oil, hydrogenating said extract at a temperature in the range 60G-850 F. and a pressure in the range 750-3,000 p.s.i.g. in the presence of a solid hydrogenation catalyst to yield a hydrogenated extract having a viscosity index at least 20 V.I. numbers greater than the aforesaid extract before hydrogenation, subsequently hydrogenating said hydrogenated extract at a temperature in the range 40G-650 F. and a pressure in the range 7503,000 p.s.i.g. in the presence of another solid hydrogenation catalyst to improve the oxidation stability of said hydrogenated extract and recovering at least a portion of the resulting hydrogenated extract as product.

8. A process in accordance with claim 7 wherein the rst aforementioned solid hydrogenation catalyst is a solid cobalt molybdate containing catalyst and wherein the other. hydrogenation catalyst comprises platinum, alumina and a combined halogen.

References Cited in the tile of this patent UNITED STATES PATENTS 1,949,231 Young Feb. 27, 1934 2,079,911 Keith et al. May 11, 1937 2,191,972 Ocon Feb. 27, 1940 2,459,465 Smith Jan. 18, 1949 2,660,552 Blanding Nov. 24, 1953 2,767,131 Iezl et al. Oct. 16, 1956 2,779,713 Cole et al. Jan. 29, 1957 2,787,582 Watkins et al. Apr. 2, 1957 2,790,754 Johnston et al. Apr. 30, 1957 2,875,145 Annable et al. Feb. 24, 1959 2,898,286 Kleinholz Aug. 4, 1959 

1. A METHOD OF TREATING AN ASPHALT-FREE WAXY HYDROCARBON FRACTION WHICH COMPRISES SOLVENT DEWAXING SAID FRACTION TO YIELD A DEWAXED OIL, SOLVENT REFINING SAID DEWAXED OIL BY CONTACT WITH A LIQUID SELECTIVE SOLVENT FOR AROMATIC HYDROCARBONS WHICH IS AT LEAST PARTIALLY IMMISCIBLE WITH SAID OIL TO PRODUCE A RAFFINTE FRACTION HAVING A RELATIVELY HIGH VISCOSITY INDEX AND A REDUCED AROMATIC CONTENT AND AN EXTRACT FRACTION HAVING A RELATIVELY LOW VISCOSITY INDEX AND AN INCREASED AROMATIC CONTENT, RECOVERING SAID RAFFINATE FRACTION, HYDROGENATING SAID EXTRACT FRACTION TO IMPROVE SUBSTANTIALLY ITS VISCOSITY INDEX BY AT LEAST ABOUT 20 V.I. NUMBERS, FRACTIONATING THE RESULTING HYDROGENATED EXTRACT FRACTION TO REMOVE THEREFROM RELATIVELY LOW BOILING HYDROCARBONS AND RECOVERING THE RESULTING FRACTIONATED HYDROGENATED EXTRACT FRACTION AS A LUBRICATING OIL PRODUCT. 